1. Field
This disclosure relates generally to semiconductors, and more specifically, to semiconductor circuits that implement counting circuitry.
2. Related Art
Population count (“popcount”) circuits function to output the number of logic “1” bits in data such as an input word or a vector value. For example, a population count is performed on a vector to determine the amount of nonzero elements within the vector. This function is useful for a variety of purposes including the testing or checking for failures in the expected operation of an integrated circuit, such as a communications processor or a memory. For data vectors containing a large number of bits, such as sixty-four or one hundred twenty-eight bits, the circuitry and the total delay required to perform the counting of the logic “1” bits is typically very large and inefficient. Significant time delays for a popcount operation are unacceptable in many applications such as high speed communication systems. In addition to the delay associated with known population count circuits, a large amount of circuit area is required to implement population counts of large data values. The extra circuit area results in additional costs where additional area can be afforded. In portable wireless applications, the additional area is prohibitive and thus the population count function cannot be implemented. In either situation, where a large number of sample points is required to be checked, the accumulation of a total count of bits of predetermined logic value is costly and time inefficient.